The disclosure of Japanese Patent Application No. 2000-200116 filed on Jun. 28, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to an in-cylinder injection type spark-ignition internal combustion engine and method of operating same.
2. Description of Related Art
There is a known in-cylinder injection type spark-ignition internal combustion engine, in which a fuel is injected directly into each cylinder of the engine during a latter half of a compression stroke. This may provide a fine combustible air-fuel mixture concentrated around a spark plug, which allows a stratified charge combustion that assures combustion of the air-fuel mixture within the cylinder while keeping an overall air-fuel ratio of the air-fuel mixture lean. In such an in-cylinder injection type spark-ignition internal combustion engine, each of the cylinders is provided with a fuel injection valve for injecting a highly pressurized fuel stored in an accumulator into the cylinder. This arrangement makes it possible to inject the fuel into the cylinder at the air pressure increased in the latter half of the compression stroke.
The fuel stored in the accumulator is pressurized by a high-pressure pump driven by the engine. However, the high-pressure pump does not operate sufficiently at the engine start-up, resulting in insufficient pressurization of the fuel in the accumulator. Generally, the in-cylinder injection type spark-ignition internal combustion engine is arranged to inject the fuel into each cylinder during an intake stroke so as to conduct a uniform combustion at the engine start-up. Since the air pressure in the cylinder during the intake stroke is lower than that during the latter half of the compression stroke, this arrangement is favorable for the fuel injection. However, the fuel pressure in the accumulator at the engine start-up is too low to successively inject an increased amount of the fuel required at the engine start-up into the cylinders. As a result, the required amount of the fuel cannot be injected to each of the cylinders, causing misfire and failing to realize the desired engine start-up.
JP-A-11-229926 discloses an in-cylinder injection type spark-ignition internal combustion engine in which the fuel injection is performed only to at least a selected cylinder at the engine start-up so as to be operated until the engine start-up is completed. According to this type of the combustion engine, the required amount of the fuel may be injected into the selected cylinder for complete combustion, resulting in good engine start-up.
Upon starting the engine, it is generally required to warm up and activate a catalyst device disposed in the engine exhaust system as early and quickly as possible. To cope with the aforementioned requirement, an exhaust gas temperature is increased by retarding the ignition timing. However, the foregoing warm-up control may deteriorate the combustion condition. When operating the selected cylinder to start the engine, the resultant output generated by the cylinder may be decreased. The small increase in the engine speed may deteriorate the engine start-up performance.
It is therefore an object of the invention to provide an in-cylinder injection type spark-ignition internal combustion engine and method of operating same which makes it possible to perform favorable engine start-up, and to warm up the catalyst device in the engine exhaust system without decreasing the engine output.
To accomplish the above and/or other objects, a first aspect of the invention provides an in-cylinder injection spark-ignition internal combustion engine including a plurality of cylinders and a catalyst device disposed in an exhaust system of the engine, in which a fuel is injected to at least one selected cylinder selected from the plurality of cylinders to be operated, and subsequently the fuel is injected to all cylinders to be operated. A variable of warm-up control to the catalyst device for the selected cylinder is smaller than that used when all cylinders are operated. In the engine according to the first aspect of the invention, the warm-up control of the catalyst device in the engine exhaust system is conducted at the engine start-up at a relatively earlier stage. Further, the warm-up controlled variable is kept to a small value during operation of the selected cylinder. This is effective to restrict the decrease in the engine output, thus providing favorable start-up of the engine.
In an in-cylinder injection spark-ignition internal combustion engine including a plurality of cylinders and a catalyst device disposed in an exhaust system of the engine, a fuel is injected to at least one selected cylinder selected from the plurality of cylinders to be operated, and subsequently the fuel is injected to all cylinders to be operated. According to a second aspect of the invention, the all cylinder operation is started and the warm-up control is started for all cylinders to warm up the catalyst device disposed in the exhaust system of the engine when a fuel injection pressure exceeds a target value. In the engine according to the second aspect of the invention, the warm-up control of the catalyst device in the engine exhaust system is not conducted during operation of the selected cylinder. This is effective to restrict the decrease in the engine output, thus providing favorable start-up of the engine. Additionally, this may realize reliable fuel injection at a high pressure while operating all cylinders with a reduced discharge amount of harmful materials.